The psychiatric side effects of exogenous corticosteroids, such as prednisone, have been described for over forty years, but not well characterized. The limited data available suggest that psychosis and mood symptoms are common, though risk factors are not known. The symptoms appear strikingly similar to those observed in bipolar disorder. This study will investigate the effects of standard medical boluses of corticosteroids in patients with asthma using structured clinical interviews and standard psychiatric rating scales. The effects of multiple courses and risk factors for developing symptoms will be explored. This investigation will provide valuable data on the frequency and nature of mood symptoms with corticosteroids, and will be the first to examine the effects of multiple courses. If the symptomatology does in fact closely parallel that seen in bipolar disorder, the effects of corticosteroids could provide the first satisfactory model for this severe illness.